Just had a look on this article again. Laws like the one used to get this kid off the hook are state-based, and it's Florida. Florida's kind of a strange state like that.
Texas has some pretty dumb laws too, for example, you're allowed to defend your home against an intruder with lethal force. There have been numerous cases where someone broke into a house, got shot and killed, and the person who killed them wasn't prosecuted.